In French, "c'est" and "il est" are both used to express qualities or characteristics about a specific person or thing. The main difference between the two is that "c'est" is used with nouns and "il est" is used with adjectives.
Let's look at your examples:
1. ____est japonais.
Here, we are describing someone's nationality, which is a noun. Therefore, we would use "c'est." The correct sentence would be: "C'est japonais."
2. ____est etudiante.
This sentence is describing someone's occupation, which is a noun. So again, we would use "c'est." The correct sentence would be: "C'est étudiante."
3. ____est un personne calme et sociable.
In this case, we are using adjectives to describe the person, so we would use "il est." The correct sentence would be: "Il est une personne calme et sociable."
Now, let's move on to your second question:
In French, "a" and "est" are used to express different things. "A" is used to express possession, while "est" is used to express a state or condition.
Let's look at your example sentence:
Elle ____ un ami sympathique.
Here, we are expressing possession, as in having a friend. Therefore, we would use "a." The correct sentence would be: "Elle a un ami sympathique."
Remember, learning a language takes practice, so keep using these expressions and paying attention to their usage in different contexts.